1. Field of the Invention
This invention relates to a membrane in general, and in particularly but not exclusively, to a membrane able to compensate for downhole effects on a volume of oil.
2. Description of the Known Prior Art
In downhole tools such as logging or drilling tools used for hydrocarbon exploration and production, it is a typical part of the tool design to have a pad that is aligned adjacent a wall of the borehole. The pad is equipped with sensors that scan the formation in the borehole wall. However, the pad itself is exposed to huge large pressures and temperatures downhole.
Thus, in formation evaluation, pad tools always face the same issue, which is they the inability withstand the absolute pressure. As such, the pads are filled with oil and compensated for by the oil expansion in temperature and shrinkage in pressure.
Today solutions for compensation systems are piston compensations, rubber membranes and metallic bellows. All those solutions encounter failures: piston tend to gall, rubber membranes are permeable to gas and bellows trap mud that block any movement resulting in mud entry into the pad. Some metal plates have sometimes been used but only to compensate for very small volumes.
It is therefore desirable to have a metal membrane that will overcomes these issues and compensates for large oil volumes.